Aortic Dissection Repair: Tips and Tricks

Patient presentation
The patient was a 67-year-old man who presented with an acute onset of chest and back pain in the setting of a hypertensive crisis. Past medical history included hypertension, obstructive sleep apnea, chronic obstructive pulmonary disease, rheumatoid arthritis, and a recent pulmonary embolism. A CT angiogram demonstrated a DeBakey type 1 aortic dissection from the aortic root the aortic bifurcation with a primary entry tear in the ascending aorta. There was no clinical or radiographic evidence of malperfusion. The patient was started on anti-impulse therapy and taken emergently to the OR for definitive surgical repair.

Preoperative imaging
Relevant findings on preoperative imaging included the location of primary entry tear, evidence of pericardial effusion, dissection involvement of the right axillary artery (which is uncommon), and radiographic evidence of malperfusion. Transesophageal echocardiogram was used to confirm the diagnosis and can identify complications such as acute aortic regurgitation, coronary malperfusion, and cardiac tamponade.

Conduct of operation
General anesthesia was performed. Bilateral radial arterial lines, a central venous catheter, pulmonary artery catheter, and transesophageal echo probe were placed. A femoral arterial line prior to sternotomy was recommended. In cases of cardiac tamponade, the patient is prepped and draped prior to general anesthesia as the patient may arrest on induction.

The right axillary artery is an ideal option for antegrade systemic arterial perfusion in hemodynamically stable patients. In unstable patients, the authors prefer to place an aortic cannula directly in the ascending aorta over a wire using Seldinger technique and TEE to confirm cannula placement in the true lumen. They avoid femoral cannulation due to the uncertain nature of false lumen dynamic changes with retrograde blood flow; however, in emergent situations, this is an expeditious approach to placing a patient on cardiopulmonary bypass.

Right axillary cannulation
They started by making a 5 cm incision in the right deltopectoral groove. The pectoralis major was retracted medially and the pectoralis minor was divided, thus exposing an aortic fat pad. The brachial plexus lies below this fat. Palpation of the axillary artery at this point helps to identify its course. The axillary artery was mobilized proximally and distally and encircled with a vessel loop for control. They give a 5000-unit heparin bolus prior to placing a side-biting clamp on the artery. They avoid the use of straight clamps, as these clamps can inadvertently injure the posterior brachial plexus branches. An arteriotomy was made to accommodate an 8 mm polyester graft, which was anastomosed in an end to side fashion to the artery using a 5-0 polypropylene suture. Once hemostasis was achieved, the graft was de-aired and attached to a dedicated aortic perfusion line for the right axillary arterial inflow. In the authors' perfusion set-up, they also used a separate arterial line which was used for re-establishment of central arterial perfusion after the distal anastomosis was completed.

Sternotomy and cannulation
A generous sternal incision was made to allow access to the aortic arch. Next a median sternotomy was performed. It is important to open the pericardium slowly in patients with cardiac tamponade, as relieving the pressure too quickly can acutely elevate the blood pressure and lead to aortic rupture. They gave full-dose system heparin (300U/kg) and placed a triple stage venous cannula in the right atrium. A retrograde cardioplegia catheter was placed in the coronary sinus. The base of the innominate artery is snared using an umbilical tape and red rubber catheter for future antegrade cerebral perfusion.

Cardiopulmonary bypass and arresting the heart
Once on full cardiopulmonary bypass, the patient was cooled to moderate hypothermia (20 - 28°C). A left ventricular vent was placed through the right superior pulmonary vein. The aortic cross-clamp was applied. Retrograde cardioplegia was delivered through the coronary sinus catheter. The aorta was then transected above the sinotubular junction. The primary entry tear was identified and is usually just distal to the sinotubular junction. The authors' first goal was to identify the left and right coronary ostia in order to deliver antegrade cardioplegia directly down the coronary arteries using ostial cannulas. They provide cold blood hyperkalemic cardioplegia every 15 minutes during the conduct of the operation. After the heart was arrested, they mobilized the aortic root. By dissecting along the right PA, one can mobilize the aortic root while remaining safely above posterior structures (i.e. left main coronary artery and left atrium). One often encounters hematoma here, but it is important to adequately mobilize the aortic root so that an anastomosis may be made at the level of the sinotubular junction. The aortic root and aortic valve were then analyzed. If the dissection tear does not extend into the root then it can be reconstructed and the aortic valve resuspended to correct aortic regurgitation. If the dissection tear does extend below the level of the sinotubular junction, then an aortic root replacement will likely need to be performed.

Distal aorta open anastomosis (hemiarch)
Once the authors have achieved an adequate temperature, they performed a circulatory arrest time-out. This includes ensuring that the appropriate staff are in the room, circulatory arrest medications have been given, neuromonitoring devices are ready, and that all preparations have been made for antegrade cerebral perfusion. Importantly, they provide an antegrade dose of cardioplegia prior to circulatory arrest. An open distal anastomosis was performed under moderate hypothermia and antegrade cerebral perfusion via the right axillary inflow. Bypass flow was stopped, the innominate artery was snared with an umbilical tape, and the cross clamp was removed. Antegrade cerebral perfusion via the R axillary inflow was run at 10 ml/kg/min (see image in video). The dissected aorta was cut to a level just proximal to the innominate artery for an open distal hemiarch anastomosis. The aortic arch was inspected for dissection tears. The authors verify backflow from the left carotid artery, which suggests an intact circle of Willis. The distal aorta was reconstructed by reapproximating the dissected layers of the aorta using two felt strips. One felt strip on the outside of adventitia was used to minimize bleeding from a repressurized false lumen. Another felt strip on the inside of the intima minimizes the risk of creating new entry tears with suturing. There are several variations for use of felt strips in aorta reconstruction. Some surgeons advocate the use of a neo-media (between dissected layers) felt strip, and some surgeons avoid felt altogether. The authors avoid the use of surgical glues in the aortic arch due to the risk of embolization.

Next, a beveled polyester graft was anastomosed to the open distal reconstruction using a 3-0 polypropylene suture. A graft sizer may be used to help determine the appropriate size graft (typically 26-30 mm graft). It is important to ensure that the graft is intussuscepted into the aorta. Once this anastomosis was complete, they re-established central arterial perfusion slowly through the side branch of the graft using a dedicated arterial line. Alternatively, if using a graft without a side-branch, the graft can be cannulated directly using perpendicular 2-0 pledgeted horizontal mattress sutures and a standard aortic cannula. After thorough de-airing, the graft was cross-clamped and central cardiopulmonary bypass was resumed. The snare was removed from the innominate artery. Typical circulatory arrest times are 20 - 25 minutes.

Aortic root reconstruction and aortic valve resuspension
While rewarming, the aortic root was re-evaluated and trimmed above the level of the sinotubular junction. The false lumen was obliterated and the dissected layers reconstructed using bio-glue, paying careful attention to avoid glue falling near the aortic valve. A 30 ml Foley balloon may be inflated within the aortic root to provide circumferential wall apposition. Some surgeons prefer an outside felt layer and inside felt layer, and others prefer a neo-media felt (between dissected layers) in order to obliterate the false lumen. Once the root was reconstructed, a pledgeted 4-0 polypropylene suture was used above each commissure to resuspend the aortic valve. Once complete, the aortic valve was tested for competence. A saline test can help identify any significant regurgitation.

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